The present invention relates to electrical shorting switch assemblies such as are used as bypass switches for electrolytic cells in a variety of electrochemical processing plants. The shorting switch assembly will typically include a plurality of hermetically sealed electrical switch members which provide electrically parallel current paths to handle the very large bypass current levels which are typically employed in electrolytic cells. Such an electrical shorting switch assembly is seen in detail in U.S. Pat. No. 4,216,359, owned by the assignee of the present invention and the teachings of which are hereby incorporated by reference. The individual electrically parallelled switches which make up the shorting switch detailed in the aforementioned patent are operated off of a common rotatable operating shaft and are more or less simultaneously opened and closed. In some cases an auxiliary arc contact switch had been employed as one of the switches of a shorting switch assembly to absorb the inductive energy of the bypassed or switched circuit. Such an auxiliary arcing switch in order to be effective must open after the other switches have opened and such a sequential switch opening can be provided by a phased cam system, such as seen in U.S. Pat. No. 4,121,268, owned by the assignee of the present invention.
The shorting switch assemblies described above utilize a rotatable shaft to reciprocate a switch opening and closing means, and this means that arc contacts which are the last to open would then be the first to close when the shorting switch is actuated to return the current to the electrolytic cell. This causes the arcing switch contacts to carry very high current loads and can occasionally result in failure of the arcing switch.
It is desirable to provide an electrica shorting switch assembly which utilizes an arcing switch in a parallel path with one or more normal current-carrying switches, with the arc switch being both a last-to-open and last-to-close switch in the assembly.
It is desirable that electrical shorting switches be latched while in the open or closed position to prevent accidental switch actuation. A positive switch actuation force should be required to open or close the shorting switch.